| Message ID | 20210512153100.285169-1-dimitri.ledkov@canonical.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | integrity: Load mokx certs from the EFI MOK config table | expand |
On Wed, May 12, 2021 at 04:31:00PM +0100, Dimitri John Ledkov wrote: > Refactor load_moklist_certs() to load either MokListRT into db, or > MokListXRT into dbx. Call load_moklist_certs() twice - first to load > mokx certs into dbx, then mok certs into db. > > This thus now attempts to load mokx certs via the EFI MOKvar config > table first, and if that fails, via the EFI variable. Previously mokx > certs were only loaded via the EFI variable. Which fails when > MokListXRT is large. Instead of large MokListXRT variable, only > MokListXRT{1,2,3} are available which are not loaded. This is the case > with Ubuntu's 15.4 based shim. This patch is required to address > CVE-2020-26541 when certificates are revoked via MokListXRT. Hi Dimitri, I don't see any problems with this technically, and based on https://bugs.launchpad.net/bugs/1928679 it looks like it is in fact needed. I suggest a change below, but I'm not sure you should make the change without confirmation from one of the maintainers that it matches what they would want. > Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring") > > Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com> > cc: keyrings@vger.kernel.org > cc: Eric Snowberg <eric.snowberg@oracle.com> > cc: Jarkko Sakkinen <jarkko@kernel.org> > cc: David Woodhouse <dwmw2@infradead.org> > cc: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serge@hallyn.com> > --- > security/integrity/platform_certs/load_uefi.c | 74 ++++++++++--------- > 1 file changed, 40 insertions(+), 34 deletions(-) > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > index f290f78c3f30..f4b913ec76e4 100644 > --- a/security/integrity/platform_certs/load_uefi.c > +++ b/security/integrity/platform_certs/load_uefi.c > @@ -66,17 +66,18 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > } > > /* > - * load_moklist_certs() - Load MokList certs > + * load_moklist_certs() - Load Mok(X)List certs > + * @load_db: Load MokListRT into db when true; MokListXRT into dbx when false > * > - * Load the certs contained in the UEFI MokListRT database into the > - * platform trusted keyring. > + * Load the certs contained in the UEFI MokList(X)RT database into the > + * platform trusted/denied keyring. > * > * This routine checks the EFI MOK config table first. If and only if > - * that fails, this routine uses the MokListRT ordinary UEFI variable. > + * that fails, this routine uses the MokList(X)RT ordinary UEFI variable. > * > * Return: Status > */ > -static int __init load_moklist_certs(void) > +static int __init load_moklist_certs(const bool load_db) Rather than passing in a bool here, I would suggest, above this function, doing something like: struct moklist_desc { const char *mokvar_name; efi_char16_t *efivar_name; const char *parse_mokvar_name; const char *parse_efivar_name; efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *); }; struct moklist_desc moklist_descriptor = { .mokvar_name = "MokListRT", .efivar_name = L"MokListRT", .parse_mokvar_name = "UEFI:MokListRT (MOKvar table)", .parse_efivar_name = "UEFI:MokListRT", .get_handler_for_guid = get_handler_for_db, }; struct moklist_desc moxklist_descriptor = { .mokvar_name = "MokListXRT", .efivar_name = L"MokListXRT", .parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)", .parse_efivar_name = "UEFI:MokListXRT", .get_handler_for_guid = get_handler_for_dbx, }; And pass each of those into load_moklist_certs() once. > { > struct efi_mokvar_table_entry *mokvar_entry; > efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; > @@ -84,41 +85,55 @@ static int __init load_moklist_certs(void) > unsigned long moksize; > efi_status_t status; > int rc; > + const char *mokvar_name = "MokListRT"; > + /* Should be const, but get_cert_list() doesn't have it as const yet */ > + efi_char16_t *efivar_name = L"MokListRT"; > + const char *parse_mokvar_name = "UEFI:MokListRT (MOKvar table)"; > + const char *parse_efivar_name = "UEFI:MokListRT"; > + efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *) = get_handler_for_db; > + > + if (!load_db) { > + mokvar_name = "MokListXRT"; > + efivar_name = L"MokListXRT"; > + parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)"; > + parse_efivar_name = "UEFI:MokListXRT"; > + get_handler_for_guid = get_handler_for_dbx; > + } > > /* First try to load certs from the EFI MOKvar config table. > * It's not an error if the MOKvar config table doesn't exist > * or the MokListRT entry is not found in it. > */ > - mokvar_entry = efi_mokvar_entry_find("MokListRT"); > + mokvar_entry = efi_mokvar_entry_find(mokvar_name); > if (mokvar_entry) { > - rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)", > + rc = parse_efi_signature_list(parse_mokvar_name, > mokvar_entry->data, > mokvar_entry->data_size, > - get_handler_for_db); > + get_handler_for_guid); > /* All done if that worked. */ > if (!rc) > return rc; > > - pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n", > - rc); > + pr_err("Couldn't parse %s signatures from EFI MOKvar config table: %d\n", > + mokvar_name, rc); > } > > /* Get MokListRT. It might not exist, so it isn't an error > * if we can't get it. > */ > - mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status); > + mok = get_cert_list(efivar_name, &mok_var, &moksize, &status); > if (mok) { > - rc = parse_efi_signature_list("UEFI:MokListRT", > - mok, moksize, get_handler_for_db); > + rc = parse_efi_signature_list(parse_efivar_name, > + mok, moksize, get_handler_for_guid); > kfree(mok); > if (rc) > - pr_err("Couldn't parse MokListRT signatures: %d\n", rc); > + pr_err("Couldn't parse %s signatures: %d\n", mokvar_name, rc); > return rc; > } > if (status == EFI_NOT_FOUND) > - pr_debug("MokListRT variable wasn't found\n"); > + pr_debug("%s variable wasn't found\n", mokvar_name); > else > - pr_info("Couldn't get UEFI MokListRT\n"); > + pr_info("Couldn't get UEFI %s\n", mokvar_name); > return 0; > } > > @@ -132,9 +147,8 @@ static int __init load_moklist_certs(void) > static int __init load_uefi_certs(void) > { > efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID; > - efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; > - void *db = NULL, *dbx = NULL, *mokx = NULL; > - unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0; > + void *db = NULL, *dbx = NULL; > + unsigned long dbsize = 0, dbxsize = 0; > efi_status_t status; > int rc = 0; > > @@ -176,23 +190,15 @@ static int __init load_uefi_certs(void) > kfree(dbx); > } > > - mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status); > - if (!mokx) { > - if (status == EFI_NOT_FOUND) > - pr_debug("mokx variable wasn't found\n"); > - else > - pr_info("Couldn't get mokx list\n"); > - } else { > - rc = parse_efi_signature_list("UEFI:MokListXRT", > - mokx, mokxsize, > - get_handler_for_dbx); > - if (rc) > - pr_err("Couldn't parse mokx signatures %d\n", rc); > - kfree(mokx); > - } > + /* Load the MokListXRT certs */ > + rc = load_moklist_certs(false); > + if (rc) > + pr_err("Couldn't parse mokx signatures: %d\n", rc); > > /* Load the MokListRT certs */ > - rc = load_moklist_certs(); > + rc = load_moklist_certs(true); > + if (rc) > + pr_err("Couldn't parse mok signatures: %d\n", rc); > > return rc; > } > -- > 2.27.0 >
Hi, On Tue, May 18, 2021 at 3:19 PM Serge E. Hallyn <serge@hallyn.com> wrote: > > On Wed, May 12, 2021 at 04:31:00PM +0100, Dimitri John Ledkov wrote: > > Refactor load_moklist_certs() to load either MokListRT into db, or > > MokListXRT into dbx. Call load_moklist_certs() twice - first to load > > mokx certs into dbx, then mok certs into db. > > > > This thus now attempts to load mokx certs via the EFI MOKvar config > > table first, and if that fails, via the EFI variable. Previously mokx > > certs were only loaded via the EFI variable. Which fails when > > MokListXRT is large. Instead of large MokListXRT variable, only > > MokListXRT{1,2,3} are available which are not loaded. This is the case > > with Ubuntu's 15.4 based shim. This patch is required to address > > CVE-2020-26541 when certificates are revoked via MokListXRT. > > Hi Dimitri, > > I don't see any problems with this technically, and based on > https://bugs.launchpad.net/bugs/1928679 it looks like it is in fact needed. > Yes it is. Also it has been pointed out to me now that debian is already applying a variation of this bugfix at https://salsa.debian.org/kernel-team/linux/-/blob/master/debian/patches/features/all/db-mok-keyring/0002-MODSIGN-load-blacklist-from-MOKx.patch The path there is similar to mine, but passes the various static values as args without a struct. Which looks clean enough. I can do a variation of a rebased patch similar to what Ben is already applying in Debian. I reached out to them, and they are not interested in upstreaming this themselves right now. > I suggest a change below, but I'm not sure you should make the change > without confirmation from one of the maintainers that it matches what > they would want. > > > Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring") > > > > Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com> > > cc: keyrings@vger.kernel.org > > cc: Eric Snowberg <eric.snowberg@oracle.com> > > cc: Jarkko Sakkinen <jarkko@kernel.org> > > cc: David Woodhouse <dwmw2@infradead.org> > > cc: David Howells <dhowells@redhat.com> > > Acked-by: Serge Hallyn <serge@hallyn.com> > > > --- > > security/integrity/platform_certs/load_uefi.c | 74 ++++++++++--------- > > 1 file changed, 40 insertions(+), 34 deletions(-) > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > index f290f78c3f30..f4b913ec76e4 100644 > > --- a/security/integrity/platform_certs/load_uefi.c > > +++ b/security/integrity/platform_certs/load_uefi.c > > @@ -66,17 +66,18 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > } > > > > /* > > - * load_moklist_certs() - Load MokList certs > > + * load_moklist_certs() - Load Mok(X)List certs > > + * @load_db: Load MokListRT into db when true; MokListXRT into dbx when false > > * > > - * Load the certs contained in the UEFI MokListRT database into the > > - * platform trusted keyring. > > + * Load the certs contained in the UEFI MokList(X)RT database into the > > + * platform trusted/denied keyring. > > * > > * This routine checks the EFI MOK config table first. If and only if > > - * that fails, this routine uses the MokListRT ordinary UEFI variable. > > + * that fails, this routine uses the MokList(X)RT ordinary UEFI variable. > > * > > * Return: Status > > */ > > -static int __init load_moklist_certs(void) > > +static int __init load_moklist_certs(const bool load_db) > > Rather than passing in a bool here, I would suggest, above this function, > doing something like: > > struct moklist_desc { > const char *mokvar_name; > efi_char16_t *efivar_name; > const char *parse_mokvar_name; > const char *parse_efivar_name; > efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *); > }; > > struct moklist_desc moklist_descriptor = { > .mokvar_name = "MokListRT", > .efivar_name = L"MokListRT", > .parse_mokvar_name = "UEFI:MokListRT (MOKvar table)", > .parse_efivar_name = "UEFI:MokListRT", > .get_handler_for_guid = get_handler_for_db, > }; > > struct moklist_desc moxklist_descriptor = { > .mokvar_name = "MokListXRT", > .efivar_name = L"MokListXRT", > .parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)", > .parse_efivar_name = "UEFI:MokListXRT", > .get_handler_for_guid = get_handler_for_dbx, > }; > > And pass each of those into load_moklist_certs() once. > > > { > > struct efi_mokvar_table_entry *mokvar_entry; > > efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; > > @@ -84,41 +85,55 @@ static int __init load_moklist_certs(void) > > unsigned long moksize; > > efi_status_t status; > > int rc; > > + const char *mokvar_name = "MokListRT"; > > + /* Should be const, but get_cert_list() doesn't have it as const yet */ > > + efi_char16_t *efivar_name = L"MokListRT"; > > + const char *parse_mokvar_name = "UEFI:MokListRT (MOKvar table)"; > > + const char *parse_efivar_name = "UEFI:MokListRT"; > > + efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *) = get_handler_for_db; > > + > > + if (!load_db) { > > + mokvar_name = "MokListXRT"; > > + efivar_name = L"MokListXRT"; > > + parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)"; > > + parse_efivar_name = "UEFI:MokListXRT"; > > + get_handler_for_guid = get_handler_for_dbx; > > + } > > > > /* First try to load certs from the EFI MOKvar config table. > > * It's not an error if the MOKvar config table doesn't exist > > * or the MokListRT entry is not found in it. > > */ > > - mokvar_entry = efi_mokvar_entry_find("MokListRT"); > > + mokvar_entry = efi_mokvar_entry_find(mokvar_name); > > if (mokvar_entry) { > > - rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)", > > + rc = parse_efi_signature_list(parse_mokvar_name, > > mokvar_entry->data, > > mokvar_entry->data_size, > > - get_handler_for_db); > > + get_handler_for_guid); > > /* All done if that worked. */ > > if (!rc) > > return rc; > > > > - pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n", > > - rc); > > + pr_err("Couldn't parse %s signatures from EFI MOKvar config table: %d\n", > > + mokvar_name, rc); > > } > > > > /* Get MokListRT. It might not exist, so it isn't an error > > * if we can't get it. > > */ > > - mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status); > > + mok = get_cert_list(efivar_name, &mok_var, &moksize, &status); > > if (mok) { > > - rc = parse_efi_signature_list("UEFI:MokListRT", > > - mok, moksize, get_handler_for_db); > > + rc = parse_efi_signature_list(parse_efivar_name, > > + mok, moksize, get_handler_for_guid); > > kfree(mok); > > if (rc) > > - pr_err("Couldn't parse MokListRT signatures: %d\n", rc); > > + pr_err("Couldn't parse %s signatures: %d\n", mokvar_name, rc); > > return rc; > > } > > if (status == EFI_NOT_FOUND) > > - pr_debug("MokListRT variable wasn't found\n"); > > + pr_debug("%s variable wasn't found\n", mokvar_name); > > else > > - pr_info("Couldn't get UEFI MokListRT\n"); > > + pr_info("Couldn't get UEFI %s\n", mokvar_name); > > return 0; > > } > > > > @@ -132,9 +147,8 @@ static int __init load_moklist_certs(void) > > static int __init load_uefi_certs(void) > > { > > efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID; > > - efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; > > - void *db = NULL, *dbx = NULL, *mokx = NULL; > > - unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0; > > + void *db = NULL, *dbx = NULL; > > + unsigned long dbsize = 0, dbxsize = 0; > > efi_status_t status; > > int rc = 0; > > > > @@ -176,23 +190,15 @@ static int __init load_uefi_certs(void) > > kfree(dbx); > > } > > > > - mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status); > > - if (!mokx) { > > - if (status == EFI_NOT_FOUND) > > - pr_debug("mokx variable wasn't found\n"); > > - else > > - pr_info("Couldn't get mokx list\n"); > > - } else { > > - rc = parse_efi_signature_list("UEFI:MokListXRT", > > - mokx, mokxsize, > > - get_handler_for_dbx); > > - if (rc) > > - pr_err("Couldn't parse mokx signatures %d\n", rc); > > - kfree(mokx); > > - } > > + /* Load the MokListXRT certs */ > > + rc = load_moklist_certs(false); > > + if (rc) > > + pr_err("Couldn't parse mokx signatures: %d\n", rc); > > > > /* Load the MokListRT certs */ > > - rc = load_moklist_certs(); > > + rc = load_moklist_certs(true); > > + if (rc) > > + pr_err("Couldn't parse mok signatures: %d\n", rc); > > > > return rc; > > } > > -- > > 2.27.0 > >
diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c index f290f78c3f30..f4b913ec76e4 100644 --- a/security/integrity/platform_certs/load_uefi.c +++ b/security/integrity/platform_certs/load_uefi.c @@ -66,17 +66,18 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, } /* - * load_moklist_certs() - Load MokList certs + * load_moklist_certs() - Load Mok(X)List certs + * @load_db: Load MokListRT into db when true; MokListXRT into dbx when false * - * Load the certs contained in the UEFI MokListRT database into the - * platform trusted keyring. + * Load the certs contained in the UEFI MokList(X)RT database into the + * platform trusted/denied keyring. * * This routine checks the EFI MOK config table first. If and only if - * that fails, this routine uses the MokListRT ordinary UEFI variable. + * that fails, this routine uses the MokList(X)RT ordinary UEFI variable. * * Return: Status */ -static int __init load_moklist_certs(void) +static int __init load_moklist_certs(const bool load_db) { struct efi_mokvar_table_entry *mokvar_entry; efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; @@ -84,41 +85,55 @@ static int __init load_moklist_certs(void) unsigned long moksize; efi_status_t status; int rc; + const char *mokvar_name = "MokListRT"; + /* Should be const, but get_cert_list() doesn't have it as const yet */ + efi_char16_t *efivar_name = L"MokListRT"; + const char *parse_mokvar_name = "UEFI:MokListRT (MOKvar table)"; + const char *parse_efivar_name = "UEFI:MokListRT"; + efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *) = get_handler_for_db; + + if (!load_db) { + mokvar_name = "MokListXRT"; + efivar_name = L"MokListXRT"; + parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)"; + parse_efivar_name = "UEFI:MokListXRT"; + get_handler_for_guid = get_handler_for_dbx; + } /* First try to load certs from the EFI MOKvar config table. * It's not an error if the MOKvar config table doesn't exist * or the MokListRT entry is not found in it. */ - mokvar_entry = efi_mokvar_entry_find("MokListRT"); + mokvar_entry = efi_mokvar_entry_find(mokvar_name); if (mokvar_entry) { - rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)", + rc = parse_efi_signature_list(parse_mokvar_name, mokvar_entry->data, mokvar_entry->data_size, - get_handler_for_db); + get_handler_for_guid); /* All done if that worked. */ if (!rc) return rc; - pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n", - rc); + pr_err("Couldn't parse %s signatures from EFI MOKvar config table: %d\n", + mokvar_name, rc); } /* Get MokListRT. It might not exist, so it isn't an error * if we can't get it. */ - mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status); + mok = get_cert_list(efivar_name, &mok_var, &moksize, &status); if (mok) { - rc = parse_efi_signature_list("UEFI:MokListRT", - mok, moksize, get_handler_for_db); + rc = parse_efi_signature_list(parse_efivar_name, + mok, moksize, get_handler_for_guid); kfree(mok); if (rc) - pr_err("Couldn't parse MokListRT signatures: %d\n", rc); + pr_err("Couldn't parse %s signatures: %d\n", mokvar_name, rc); return rc; } if (status == EFI_NOT_FOUND) - pr_debug("MokListRT variable wasn't found\n"); + pr_debug("%s variable wasn't found\n", mokvar_name); else - pr_info("Couldn't get UEFI MokListRT\n"); + pr_info("Couldn't get UEFI %s\n", mokvar_name); return 0; } @@ -132,9 +147,8 @@ static int __init load_moklist_certs(void) static int __init load_uefi_certs(void) { efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID; - efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; - void *db = NULL, *dbx = NULL, *mokx = NULL; - unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0; + void *db = NULL, *dbx = NULL; + unsigned long dbsize = 0, dbxsize = 0; efi_status_t status; int rc = 0; @@ -176,23 +190,15 @@ static int __init load_uefi_certs(void) kfree(dbx); } - mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status); - if (!mokx) { - if (status == EFI_NOT_FOUND) - pr_debug("mokx variable wasn't found\n"); - else - pr_info("Couldn't get mokx list\n"); - } else { - rc = parse_efi_signature_list("UEFI:MokListXRT", - mokx, mokxsize, - get_handler_for_dbx); - if (rc) - pr_err("Couldn't parse mokx signatures %d\n", rc); - kfree(mokx); - } + /* Load the MokListXRT certs */ + rc = load_moklist_certs(false); + if (rc) + pr_err("Couldn't parse mokx signatures: %d\n", rc); /* Load the MokListRT certs */ - rc = load_moklist_certs(); + rc = load_moklist_certs(true); + if (rc) + pr_err("Couldn't parse mok signatures: %d\n", rc); return rc; }
Refactor load_moklist_certs() to load either MokListRT into db, or MokListXRT into dbx. Call load_moklist_certs() twice - first to load mokx certs into dbx, then mok certs into db. This thus now attempts to load mokx certs via the EFI MOKvar config table first, and if that fails, via the EFI variable. Previously mokx certs were only loaded via the EFI variable. Which fails when MokListXRT is large. Instead of large MokListXRT variable, only MokListXRT{1,2,3} are available which are not loaded. This is the case with Ubuntu's 15.4 based shim. This patch is required to address CVE-2020-26541 when certificates are revoked via MokListXRT. Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring") Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com> cc: keyrings@vger.kernel.org cc: Eric Snowberg <eric.snowberg@oracle.com> cc: Jarkko Sakkinen <jarkko@kernel.org> cc: David Woodhouse <dwmw2@infradead.org> cc: David Howells <dhowells@redhat.com> --- security/integrity/platform_certs/load_uefi.c | 74 ++++++++++--------- 1 file changed, 40 insertions(+), 34 deletions(-)